Personalized dosing via pharmacokinetic monitoring of 5-fluorouracil might reduce toxicity in early- or late-stage colorectal cancer patients treated with infusional 5-fluorouracil-based chemotherapy regimens

Drug monitoring detects under- and overdosing in patients receiving 5-fluorouracil-containing chemotherapy-results of a prospective, multicenter German observational study

INTRODUCTION

Body surface area (BSA)-based dosing of 5-fluorouracil (5-FU) results in marked inter-individual variability in drug levels, whereas determination of plasma 5-FU concentration and area under the curve (AUC) is a more precise dosing method but has not been integrated into clinical routine. We conducted a multicenter, prospective study to study 5-FU AUC distributions and assess clinical factors predicting therapeutic dosing in patients receiving BSA-dosed 5-FU.

METHODS

Between June 2017 and January 2018, a total of 434 patients receiving continuous, infusional BSA-dosed 5-FU from 37 sites in Germany were included. Plasma 5-FU concentration and AUC were measured in venous blood samples at steady state. The primary objective was to determine 5-FU AUC distributions in relation to the target range, which is defined as 20-30 mg × h/l. The second objective was to explore clinical parameters that correlate with achievement of 5-FU AUC target range.

RESULTS

The primary tumor was mainly located in the gastrointestinal tract (96.3%), with colorectal cancer being the most common (71.2%) tumor entity. 5-FU was administered as monotherapy (8.1%) or as part of FOLFOX (33.2%), FOLFIRI (26.3%), or other regimens (12.4%). Treatment setting was adjuvant (31.3%) or metastatic (64.5%). The median AUC was 16 mg × h/l. Only 20.3% of patients received 5-FU treatment within the target range, whereas the majority of patients (60.6%) were underdosed and 19.1% of patients were overdosed. In the univariate logistic regression, treatment setting was the only clinical parameter that significantly correlated with achievement of the target range. Patients treated in the metastatic setting had a 2.1 (95% confidence interval 1.186-3.776, P = 0.011) higher odds to reach the target range compared with patients treated in the adjuvant setting.

CONCLUSIONS

The majority of patients received suboptimal doses of 5-FU using BSA dosing. Therapeutic drug monitoring of 5-FU is an option for optimized individualized cancer therapy and should be integrated into the clinical practice.

Therapeutic drug monitoring of neoadjuvant mFOLFIRINOX in resected pancreatic ductal adenocarcinoma

BACKGROUND

Despite a potentially curative treatment, the prognosis after upfront surgery and adjuvant chemotherapy for patients with resectable pancreatic ductal adenocarcinoma (PDAC) is poor. Modified FOLFIRINOX (mFOLFIRINOX) is a cornerstone in the systemic treatment of PDAC, including the neoadjuvant setting. Pharmacokinetic-guided (PKG) dosing has demonstrated beneficial effects in other tumors, but scarce data is available in pancreatic cancer.

METHODS

Forty-six patients with resected PDAC after mFOLFIRINOX neoadjuvant approach and included in an institutional protocol for anticancer drug monitoring were retrospectively analyzed. 5-Fluorouracil (5-FU) dosage was adjusted throughout neoadjuvant treatment according to pharmacokinetic parameters and Irinotecan (CPT-11) pharmacokinetic variables were retrospectively estimated.

RESULTS

By exploratory univariate analyses, a significantly longer progression-free survival was observed for patients with either 5-FU area under the curve (AUC) above 28 mcg·h/mL or CPT-11 AUC values below 10 mcg·h/mL. In the multivariate analyses adjusted by age, gender, performance status and resectability after stratification according to both pharmacokinetic parameters, the risk of progression was significantly reduced in patients with 5-FU AUC ≥28 mcg·h/mL [HR = 0.251, 95% CI 0.096-0.656; p = 0.005] and CPT-11 AUC <10 mcg·h/mL [HR = 0.189, 95% CI 0.073-0.486, p = 0.001].

CONCLUSIONS

Pharmacokinetically-guided dose adjustment of standard chemotherapy treatments might improve survival outcomes in patients with pancreatic ductal adenocarcinoma.

The past, present, and future of chemotherapy with a focus on individualization of drug dosing

While there have been rapid advances in developing new and more targeted drugs to treat cancer, much less progress has been made in individualizing dosing. Even though the introduction of immunotherapies such as CAR T-cells and checkpoint inhibitors, as well as personalized therapies that target specific mutations, have transformed clinical treatment of cancers, chemotherapy remains a mainstay in oncology. Chemotherapies are typically dosed on either a body surface area (BSA) or weight basis, which fails to account for pharmacokinetic differences between patients. Drug absorption, distribution, metabolism, and excretion rates can vary between patients, resulting in considerable differences in exposure to the active drugs. These differences result in suboptimal dosing, which can reduce efficacy and increase side-effects. Therapeutic drug monitoring (TDM), genotype guided dosing, and chronomodulation have been developed to address this challenge; however, despite improving clinical outcomes, they are rarely implemented in clinical practice for chemotherapies. Thus, there is a need to develop interventions that allow for individualized drug dosing of chemotherapies, which can help maximize the number of patients that reach the most efficacious level of drug in the blood while mitigating the risks of underdosing or overdosing. In this review, we discuss the history of the development of chemotherapies, their mechanisms of action and how they are dosed. We discuss substantial intraindividual and interindividual variability in chemotherapy pharmacokinetics. We then propose potential engineering solutions that could enable individualized dosing of chemotherapies, such as closed-loop drug delivery systems and bioresponsive biomaterials.

A RAS-Independent Biomarker Panel to Reliably Predict Response to MEK Inhibition in Colorectal Cancer

Simple Summary

Today, clinical management for the majority of cancer patients is still based on a “one-size-fits-all” approach. To improve the outcomes in the era of personalized medicine, it is essential to stratify patients based on established and novel biomarkers. In the present study, we investigated a SMAD4 loss-of-function mutation, which is associated with chemoresistance and decreased overall survival in colorectal cancer (CRC). To investigate the molecular mechanism behind the impact on drug response, we used CRISPR technology on patient-derived organoid models (PDOs) of CRC. We showed that PDOs with loss-of-function SMAD4 mutations are sensitive to MEK-inhibitors. Using a novel four-gene signature reliably predicts sensitivity towards MEK-inhibitors, regardless of the RAS and BRAF status. The present study is a significant step towards personalized cancer therapy by identifying a new biomarker.

Abstract

Background: In colorectal cancer (CRC), mutations of genes associated with the TGF-β/BMP signaling pathway, particularly affecting SMAD4, are known to correlate with decreased overall survival and it is assumed that this signaling axis plays a key role in chemoresistance. Methods: Using CRISPR technology on syngeneic patient-derived organoids (PDOs), we investigated the role of a loss-of-function of SMAD4 in sensitivity to MEK-inhibitors. CRISPR-engineered SMAD4^R361H PDOs were subjected to drug screening, RNA-Sequencing, and multiplex protein profiling (DigiWest^®). Initial observations were validated on an additional set of 62 PDOs with known mutational status. Results: We show that loss-of-function of SMAD4 renders PDOs sensitive to MEK-inhibitors. Multiomics analyses indicate that disruption of the BMP branch within the TGF-β/BMP pathway is the pivotal mechanism of increased drug sensitivity. Further investigation led to the identification of the SFAB-signature (SMAD4, FBXW7, ARID1A, or BMPR2), coherently predicting sensitivity towards MEK-inhibitors, independent of both RAS and BRAF status. Conclusion: We identified a novel mutational signature that reliably predicts sensitivity towards MEK-inhibitors, regardless of the RAS and BRAF status. This finding poses a significant step towards better-tailored cancer therapies guided by the use of molecular biomarkers.

Current status and future outlooks on therapeutic drug monitoring of fluorouracil

INTRODUCTION

: Therapeutic drug monitoring (TDM) of the anticancer drug fluorouracil (5FU) as a method to support dose adjustments has been researched and discussed extensively. Despite manifold evidence of the advantages of 5FU-TDM, traditional body surface area (BSA)-guided dosing is still widely applied.

AREAS COVERED

: This review covers the latest evidence on 5FU-TDM based on a literature search in PubMed between June and September 2021. It particularly highlights new approaches of implementing 5FU-TDM into precision medicine by combining TDM with pharmacogenetic testing and/or pharmacometric models. This review further discusses remaining obstacles in order to incorporate 5FU-TDM into clinical routine.

EXPERT OPINION

: New data on 5FU-TDM further strengthen the advantages compared to BSA-guided dosing as it is able to reduce pharmacokinetic variability and thereby improve treatment efficacy and safety. Interprofessional collaboration has the potential to overcome the remaining barriers for its implementation. Pre-emptive pharmacogenetic testing followed by 5FU-TDM can further improve 5FU exposure in a substantial proportion of patients. Developing a model framework integrating pharmacokinetics and pharmacodynamics of 5FU will be crucial to fully advance into the precision medicine era. Model applications can potentially support clinicians in dose finding before starting chemotherapy. Additionally, TDM provides further assistance in continuously improving model predictions.

Clinical Benefit of Therapeutic Drug Monitoring in Colorectal Cancer Patients Who Received Fluorouracil-Based Chemotherapy

Background

The impact of therapeutic drug management (TDM) on reducing toxicity and improving efficacy in colorectal cancer (CRC) patients receiving fluorouracil-based chemotherapy is still unclear.

Material/Methods

A total of 207 patients (Study Group n=54, Historical Group n=153) with metastatic colorectal cancer were enrolled. All of them received 6 administrations of the 5-FU based regimens. Initial 5-FU dosing of all patients was calculated using body surface area (BSA). In the Study Group, individual exposure during each cycle was measured using a nanoparticle immunoassay, and the 5-FU blood concentration was calculated using the area under the curve (AUC). We adjusted the 5-FU infusion dose of the next cycle based on the AUC data of the previous cycle to achieve the target of 20–30 mg×h/L.

Results

In the fourth cycle, patients in the target concentration range (AUC mean, 26.3 mg×h/L; Median, 28 mg×h/L; Range, 14–38 mg×h/L; CV, 22.4%) accounted for 46.8% of all patients, which were more than the ones in the first cycle (P<0.001). 5-FU TDM significantly reduced the toxicity of chemotherapy and improved its efficacy. The Study Group (30/289) showed a lower percentage of severe adverse events than that in the Historical Group (185/447) (P<0.001). The incidences of complete response and partial response in the Study Group were higher than those in the Historical Group (P=0.032).

Conclusions

TDM in colorectal cancer can reduce toxicity, improve efficacy and clinical outcome, and can be routinely used in 5-FU-based chemotherapy.

Systemic exposure to 5-fluorouracil and its metabolite, 5,6-dihydrofluorouracil, and development of a limited sampling strategy for therapeutic drug management of 5-fluorouracil in patients with gastrointestinal malignancy

AIMS

5-Fluorouracil (5-FU) is widely used in combination chemotherapy, and literature suggests pharmacokinetic-guided dosing to improve clinical efficacy and reduce toxicity. This study aimed to determine the pharmacokinetic exposure of both 5-FU and its metabolite, 5,6-dihydrofluorouracil (DHFU), in patients with gastrointestinal malignancy and to establish a simplified strategy to assist in therapeutic drug management for dose optimization.

METHODS

This was a prospective, observational study, performed in 27 patients diagnosed with gastrointestinal malignancy who were prescribed 5-FU. Multiple samples were collected per patient over the slow bolus (15-20 min) and continuous infusion period (over 44 h) in doses 1 and 3, and the concentrations of 5-FU and DHFU were measured.

RESULTS

A higher proportion of patients had exposures within the therapeutic range in dose 3 (50%) as compared to dose 1 (37.5%) with 5-FU. There was an association between delayed time to maximum concentration of DHFU and a high maximum concentration of 5-FU. A limited sampling strategy was developed with 4 samples, 2 during the bolus period and 2 during the continuous period (at 18 h and the end of infusion), which accurately predicted the total area under the curve of 5-FU.

CONCLUSION

Using body surface area-based dosing with 5-FU, 50-60% of patients were outside of the therapeutic range. In the absence of genotype testing, measurement of the metabolite DHFU could be a phenotypical measure of dihydropyrimidine dehydrogenase enzyme activity. A limited sampling strategy was developed in patients who were prescribed a combination regimen of slow bolus, followed by a 44-hour continuous infusion of 5-FU to assist in the therapeutic drug management of patients.

Pharmacokinetics-based Dose Management of 5-Fluorouracil Clinical Research in Advanced Colorectal Cancer Treatment

Objective:

The study aimed to explore the efficacy of pharmacokinetic-based 5-fluorouracil dose management by plasma concentration test in advanced colorectal cancer treatment.

Methods:

153 samples of advanced colorectal cancer patients were enrolled and randomly assigned to a control group and an experimental group. All patients received double-week chemotherapy with 5- fluorouracil (four weeks were used as one period), and chemotherapy duration ranged from 2 to 6 periods. In the first period, all patients were administered with the classic strategy of body surface area (BSA).

Results:

In the subsequent periods, the control group (77 samples) continued with BSA guided chemotherapy, while the experimental group (76 samples) received pharmacokinetic AUC-based chemotherapy. The efficacy and toxic side effects were assessed during chemotherapy, and survival was recorded in a follow-up. In the AUC experimental group, the rate of diarrhea significantly decreased (37.50% vs. 70.00%, P=0.010), and incidence of oral mucositis reduced (54.17% vs. 82.50%, P=0.014). Compared with the control group, the clinical benefit rate of experimental group was much higher (90.79% vs. 79.22%, P=0.046).

Conclusion:

There was no significant difference in other 5-fluorouracil related toxic side effect events (nausea, vomiting, hand-foot syndrome) and progression-free survival between the two groups. Pharmacokinetic- based dose management of 5-Fluorouracil reduces the toxicity of chemotherapy and improves long-term efficacy of chemotherapy for advanced colorectal cancer patients.

How can we best monitor 5-FU administration to maximize benefit to risk ratio?

INTRODUCTION

5-Fluorouracil (5-FU) is currently used as a chemotherapy in several cancers such as head-and-neck (H&N) and colorectal cancers. 5-FU dosing is traditionally based on body surface area (BSA), but this strategy is usually associated with severe toxicities. 5-FU is mainly catabolized by dihydropyrimidine dehydrogenase (DPD), and 5-FU dosage adaptation according to DPD status at the first cycle of treatment is now recommended. To further optimize 5-FU-based chemotherapy, a body of evidences justifies therapeutic drug monitoring (TDM). Areas covered: 5-FU pharmacokinetics, relationships between pharmacokinetics and efficacy or toxicity of 5-FU, proofs of interest of 5-FU TDM and its practical considerations are discussed. Expert opinion: BSA-adjusted 5-FU administration is associated with a large inter-individual variability, and according to this strategy, many patients experience under- or overexposure. Moreover, relationships between 5-FU area under the curve (AUC) and its toxicity or efficacy have been demonstrated, at least in patients with colorectal or H&N cancers. 5-FU therapeutic index has been validated and algorithms of 5-FU dosage adaptation according to its AUC are now available. Advances in pre-analytical and analytical steps of 5-FU TDM make its use feasible in clinical practice. Thus, there are consistent evidences to recommend 5-FU TDM in patients with advanced colorectal or H&N cancers.

A novel approach to the application of hexagonal mesoporous silica in solid-phase extraction of drugs

Mesoporous silica with hexagonal type structure containing amine functional group was introduced. Firstly, aminopropyl hexagonal mesoporous silica was synthetized in a co-condensation process, via templating route of n-dodecylamine. Then synthesized mesoporous material were characterized, and FT-IR spectrum confirmed the presence of amine group and CHN analysis determined the amount of organic layer. The high surface area (750 m²/g) was determined by applying nitrogen adsorption-desorption technique. The morphology was examined by scanning electron microscopy which proved hexagonal structure. The crystallinity of mesoporous material was observed in XRD pattern of this material. According to previous background of such material in adsorbing drug, herein, the efficiency of this material in adsorbing of 5-fluorouracil was evaluated through solid phase extraction method in aqueous and plasma media with high performance liquid chromatography. The extraction efficiency was evaluated for drug concentrations of 500-2000 ng/ml by means of 5-20 mg/ml hexagonal mesoporous silica in both media. The results showed good to excellent recovery rate of in both aqueous and plasma medium which confirmed that the aminopropyl functionalized hexagonal mesoporous silica could be considered as promising device for drug bioanalysis.

Therapeutic Drug Monitoring in Oncology: International Association of Therapeutic Drug Monitoring and Clinical Toxicology Recommendations for 5-Fluorouracil Therapy

5-Fluorouracil (5-FU) is dosed by body surface area, a practice unable to reduce the interindividual variability in exposure. Endorsed by the International Association of Therapeutic Drug Monitoring and Clinical Toxicology (IATDMCT), we evaluated clinical evidence and strongly recommend TDM for the management of 5-FU therapy in patients with colorectal or head-and-neck cancer receiving common 5-FU regimens. Our systematic methodology provides a framework to evaluate published evidence in support of TDM recommendations in oncology.

[5-fluorouracil therapeutic drug monitoring: Update and recommendations of the STP-PT group of the SFPT and the GPCO-Unicancer]

Despite being 60-years old now, 5-FU remains the backbone of numerous regimen to treat a variety of solid tumors such as breast, head-and-neck and digestive cancers either in neo-adjuvant, adjuvant or metastatic settings. Standard 5-FU usually claims 15-40% of severe toxicities and up to 1% of toxic-death. Numerous studies show a stiff relationship between 5-FU exposure and toxicity or efficacy. In addition, 5-FU pharmacokinetics is highly variable between patients. Indeed, 80% of the 5-FU dose is catabolized in the liver by dihydropyrimidine dehydrogenase (DPD) into inactive compounds. It is now well established that DPD deficiency could lead to severe toxicities and, thus, require dose reduction in deficient patients. However, despite dosage adaptation based on DPD status, some patients may still experience under- or over-exposure, leading to inefficacy or major toxicity. The "Suivi thérapeutique pharmacologique et personnalisation des traitements" (STP-PT) group of the "Société française de pharmacologie et de thérapeutique" (SFPT) and the "Groupe de pharmacologie clinique oncologique" (GPCO)-Unicancer, based on the latest and most up-to-date literature data, recommend the implementation of 5-FU Therapeutic Drug Monitoring in order to ensure an adequate 5-FU exposure.

A correlation study of fluorouracil pharmacodynamics with clinical efficacy and toxicity

Purpose:

Plasma 5-fluorouracil (5-FU) concentrations vary greatly between individuals who have received standard dosage. Pharmacokinetic adjusted doses have been hypothesized to overcome the possibility of potential toxicity and ineffectiveness related to inappropriate plasma levels of 5-FU. In this study, we prospectively investigated the clinical benefit and toxicity of 5-FU in relation to its pharmacokinetic properties.

Methods:

Pharmacokinetics, effectiveness, and toxicity of 5-FU were investigated in 101 patients. The 5-FU pharmacokinetics were measured on day 2 of chemotherapy infusions. Clinicodemographic characteristics are outlined.

Results:

All 101 patients who received adjuvant chemotherapy were alive at the end of a median 45 months of the follow-up period. At least one grade 1 adverse event (AE) was observed in 69.3% of the patients and grade two AEs were observed in 10.1% of the patients. The 5-FU levels ranged between 103 and 4311 µg/L and area under the curve (AUC) measurements ranged between 4.5 and 189.7 mg min/L. Pharmacokinetic measurements were not significantly correlated with clinical efficacy (log-rank p = 0.21). However, higher AUC levels were positively correlated with toxicity (p = 0.02) and with the severity of adverse events. The risks of mucositis (odds ratio [OR] 1.45; p = 0.042) and neurotoxicity (OR 2.01; p = 0.009) were significantly increased in a logistic regression model.

Conclusions:

There is no clear evidence that increased plasma levels or pharmacokinetic adjusted doses of 5-FU were related to better efficacy. However, toxicity might be closely associated with increased plasma levels of 5-FU. Toxicities can be deferred via dose adjustments without any expense in efficacy.

Emerging roles for clinical pharmacometrics in cancer precision medicine

Purpose of review

Although significant progress has been made in cancer research, there exist unmet needs in patient care as reflected by the 'Cancer Moonshot' goals. This review appreciates the potential utility of quantitative pharmacology in cancer precision medicine.

Recent findings

Precision oncology has received federal funding largely due to 'The Precision Medicine Initiative'. Precision medicine takes into account the inter-individual variability, and allows for tailoring the right medication or the right dose of drug to the best subpopulation of patients who will likely respond to the intervention, thus enhancing therapeutic success and reducing "financial toxicity" to patients, families and caregivers. The National Cancer Institute (NCI) committed US$ 70 million from its fiscal year 2016 budget to advance precision oncology research. Through the 'Critical Path Initiative', pharmacometrics has gained an important role in drug development; however, it is yet to find widespread clinical applicability.

Summary

Stakeholders including clinicians and pharmacometricians need to work in concert to ensure that benefits of model-based approaches are harnessed to personalize cancer care to the individual needs of the patient via better dosing strategies, companion diagnostics, and predictive biomarkers. In medical oncology, where immediate patient care is the clinician's primary concern, pharmacometric approaches can be tailored to build models that rely on patient data already digitally available in the Electronic Health Record (EHR) to facilitate quick collaboration and avoid additional funding needs. Taken together, we offer a roadmap for the future of precision oncology which is fraught with both challenges and opportunities for pharmacometricians and clinicians alike.

A Retroviral Replicating Vector Encoding Cytosine Deaminase and 5-FC Induces Immune Memory in Metastatic Colorectal Cancer Models

Treatment of tumors with Toca 511, a gamma retroviral replicating vector encoding cytosine deaminase, followed by 5-fluorocytosine (5-FC) kills tumors by local production of 5-fluorouracil (5-FU). In brain tumor models, this treatment induces systemic anti-tumor immune responses and long-term immune-mediated survival. Phase 1 Toca 511 and Toca FC (extended-release 5-FC) clinical trials in patients with recurrent high-grade glioma show durable complete responses and promising survival data compared to historic controls. The work described herein served to expand on our earlier findings in two models of metastatic colorectal carcinoma (mCRC). Intravenous (i.v.) delivery of Toca 511 resulted in substantial tumor-selective uptake of vector into metastatic lesions. Subsequent treatment with 5-FC resulted in tumor shrinkage, improved survival, and immune memory against future rechallenge with the same CT26 CRC cell line. Similar results were seen in a brain metastasis model of mCRC. Of note, 5-FC treatment resulted in a significant decrease in myeloid-derived suppressor cells (MDSCs) in mCRC tumors in both the liver and brain. These results support the development of Toca 511 and Toca FC as a novel immunotherapeutic approach for patients with mCRC. A phase 1 study of i.v. Toca 511 and Toca FC in solid tumors, including mCRC, is currently underway (NCT02576665).

Tumor Evolution, Heterogeneity, and Therapy for Our Patients With Advanced Cancer: How Far Have We Come?

The clinical and molecular heterogeneity of various cancer types is well documented. In the era of precision oncology whereby molecular profiling of tumors is incorporated into clinical care, both intra- and intertumoral molecular and genetic heterogeneity have been described. Together, they impact patient treatment and outcomes. Host genetics and the tumor microenvironment impact on tumor evolution and heterogeneity through variations in immune cell infiltration, stromal variations, and selection pressures from hypoxia or nutrient stress, among others. Tumor progression and exposure to therapeutic agents lead to further molecular evolution and heterogeneity that is clinically relevant. Moreover, tumors that evolve after diagnosis and as a function of therapy generally become more aggressive and refractory to available therapeutics, including targeted agents and immunotherapy. The evolving clinical and molecular heterogeneity of patient tumors can be explored with various clinical and research-based specimens and testing such as pre- and post-treatment biopsies; serial liquid biopsies; single cell analysis; PDX and organoid models; anatomic, functional, and molecular imaging; and rapid postmortem studies. Other factors that influence tumor heterogeneity include immune checkpoints, cancer stem cells, therapy-acquired resistance mechanisms that may occur through secondary mutations, and adaptive responses. Modern technologic advances for tumor characterization provide opportunities to understand tumor evolution and its impact on clinical outcomes to improve therapeutic regimens. Characterization of novel targets and development of effective therapeutics are needed to target heterogeneity and the evolution of resistance mechanisms.

Fabrication and Use of Poly(d,l-lactide-co-glycolide)-Based Formulations Designed for Modified Release of 5-Fluorouracil

5-fluorouracil (5-FU) is a chemotherapeutic agent that has been used for the treatment of a variety of malignancies since its initial introduction to the clinic in 1957. Owing to its short biological half-life, multiple dosings are generally required to maintain effective 5-FU plasma concentrations throughout the therapeutic period. Clinical studies have shown that continuous 5-FU administration is generally superior to bolus injection as exhibited by lower toxicities and increased therapeutic efficacy. Optimal therapeutic efficacy, however, is often compromised by the limiting therapeutic index. Whilst oral formulations are also used, these suffer from the drawbacks of variable bioavailability and first-pass metabolism. As a result, sustained release formulations of 5-FU have been investigated in an effort to mimic the kinetics of continuous infusion particularly for situations where local delivery is considered appropriate. The biocompatible, biodegradable, and highly tunable synthetic polymer, poly(d,l-lactide-co-glycolide) (PLGA), is widely used as a vector for sustained drug delivery, however, issues such as insufficient loading and inappropriate burst release kinetics have dogged progress into the clinic for small hydrophilic drugs such as 5-FU. This review provides introductory information about the mechanism of action, pharmacokinetic and physicochemical properties, and clinical use of 5-FU that have contributed to the development of PLGA-based 5-FU release platforms. In addition, this review provides information on fabrication methods used for a range of 5-FU-loaded PLGA formulations and discusses factors affecting the release kinetics of 5-FU as well as the in vitro and in vivo antitumor or antiproliferative efficacy of these platforms.

P53 represses pyrimidine catabolic gene dihydropyrimidine dehydrogenase (DPYD) expression in response to thymidylate synthase (TS) targeting

Nucleotide metabolism in cancer cells can influence malignant behavior and intrinsic resistance to therapy. Here we describe p53-dependent control of the rate-limiting enzyme in the pyrimidine catabolic pathway, dihydropyrimidine dehydrogenase (DPYD) and its effect on pharmacokinetics of and response to 5-fluorouracil (5-FU). Using in silico/chromatin-immunoprecipitation (ChIP) analysis we identify a conserved p53 DNA-binding site (p53BS) downstream of the DPYD gene with increased p53 occupancy following 5-FU treatment of cells. Consequently, decrease in Histone H3K9AC and increase in H3K27me3 marks at the DPYD promoter are observed concomitantly with reduced expression of DPYD mRNA and protein in a p53-dependent manner. Mechanistic studies reveal inhibition of DPYD expression by p53 is augmented following thymidylate synthase (TS) inhibition and DPYD repression by p53 is dependent on DNA-dependent protein kinase (DNA-PK) and Ataxia telangiectasia mutated (ATM) signaling. In-vivo, liver specific Tp53 loss increases the conversion of 5-FU to 5-FUH₂ in plasma and elicits a diminished 5-FU therapeutic response in a syngeneic colorectal tumor model consistent with increased DPYD-activity. Our data suggest that p53 plays an important role in controlling pyrimidine catabolism through repression of DPYD expression, following metabolic stress imposed by nucleotide imbalance. These findings have implications for the toxicity and efficacy of the cancer therapeutic 5-FU.

Is monitoring of plasma 5-fluorouracil levels in metastatic / advanced colorectal cancer clinically effective? A systematic review

Background

Pharmacokinetic guided dosing of 5-fluorouracil chemotherapies to bring plasma 5-fluorouracil into a desired therapeutic range may lead to fewer side effects and better patient outcomes. High performance liquid chromatography and a high throughput nanoparticle immunoassay (My5-FU) have been used in conjunction with treatment algorithms to guide dosing. The objective of this study was to assess accuracy, clinical effectiveness and safety of plasma 5-fluorouracil guided dose regimen(s) versus standard regimens based on body surface area in colorectal cancer.

Methods

We undertook a systematic review. MEDLINE; MEDLINE In-Process & Other Non-Indexed Citations; EMBASE; Cochrane Library; Science Citation Index and Conference Proceedings (Web of Science); and NIHR Health Technology Assessment Programme were searched from inception to January 2014. We reviewed evidence on accuracy of My5-FU for estimating plasma 5-fluorouracil and on the clinical effectiveness of pharmacokinetic dosing compared to body surface area dosing. Estimates of individual patient data for overall survival and progression-free survival were reconstructed from published studies. Survival and adverse events data were synthesised and examined for consistency across studies.

Results

My5-FU assays were found to be consistent with reference liquid chromatography tandem mass spectrometry. Comparative studies pointed to gains in overall survival and in progression-free survival with pharmacokinetic dosing, and were consistent across multiple studies.

Conclusions

Although our analyses are encouraging, uncertainties remain because evidence is mainly from outmoded 5-fluorouracil regimens; a randomised controlled trial is urgently needed to investigate new dose adjustment methods in modern treatment regimens.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2581-x) contains supplementary material, which is available to authorized users.

Pharmacokinetically guided algorithm of 5-fluorouracil dosing, a reliable strategy of precision chemotherapy for solid tumors: a meta-analysis

Precision medicine characterizes a new era of cancer care and provides each patient with the right drug at the right dose and time. However, the practice of precision dosing is hampered by a lack of smart dosing algorithms. A pharmacokinetically guided (PKG) dosing algorithm is considered to be the leading strategy for precision chemotherapy, although the effects of PKG dosing are not completely confirmed. Hence, we conducted a meta-analysis to evaluate the effects of the PKG algorithm of 5-fluorouracil (5-FU) dosing on patients with solid tumors. A comprehensive retrieval was performed to identify all of the prospective controlled studies that compared the body surface area (BSA)-based algorithm with the PKG algorithm of 5-FU in patients with solid tumors. Overall, four studies with 504 patients were included. The PKG algorithm significantly improved the objective response rate of 5-FU-based chemotherapy compared with the BSA-based algorithm. Furthermore, PKG dosing markedly decreased the risk of total grade 3/4 adverse drug reactions, especially those related to hematological toxicity. Overall, the PKG algorithm may serve as a reliable strategy for individualized dosing of 5-FU.

Therapeutic drug monitoring of 5-fluorouracil. Cancer Chemother Pharmacol. 2016;78:447-464. [PMID: 27217046 DOI: 10.1007/s00280-016-3054-2]

PURPOSE

For over 50 years, 5-FU has played a critical role in the systemic chemotherapy of cancer patients. 5-FU serves as the main backbone of combination chemotherapy for patients with colorectal cancer in both the adjuvant and metastatic disease settings. Herein, we review the current status of 5-FU therapeutic drug monitoring (TDM) and discuss its potential role in the clinical practice setting.

METHOD

PubMed and abstracts from the American Society of Clinical Oncology were searched up through September 2015 for clinical data relating to 5-FU TDM.

RESULTS

5-FU dosing has been typically determined by using body surface area (BSA). However, it is now well established that BSA-based 5-FU dosing is correlated with a wide variation of 5-FU systemic exposure. Pharmacokinetic (PK) studies of 5-FU systemic exposure have shown a wide range of interpatient variation of 5-FU plasma drug levels. Over the past 30 years, increasing efforts have been placed on optimizing 5-FU dosing with the main goals of increasing antitumor efficacy while reducing drug-associated toxicity. There is growing evidence to show that 5-FU dosing based on plasma 5-FU drug level is feasible and that 5-FU TDM can improve clinical outcomes by improving efficacy of 5-FU-based combination regimens and reducing toxicities.

CONCLUSION

Dose adjustment of 5-FU is feasible, and PK-based dosing can significantly improve clinical outcomes by reducing toxicities and improving efficacy.

Effect of mFOLFOX6 chemotherapy combined with autologous CIK cells on T lymphocyte subsets in patients with advanced colorectal cancer

AIM: To observe the effect of mFOLFOX6 chemotherapy combined with autologous cytokine-induced killer (CIK) cells on T lymphocyte subsets in patients with advanced colorectal cancer.

METHODS: Eighty-nine patients with advanced colorectal cancer treated at our hospital from January 2009 to December 2014 were selected and divided into a combination group (29 cases), a chemotherapy group (30 cases) and a CIK group (30 cases) by the random comprehensive equilibrium sequential method. The chemotherapy group was given mFOLFOX6 chemotherapy alone, the CIK group was given autologous CIK cell treatment alone, and the combination group was given mFOLFOX6 chemotherapy combined with autologous CIK cell treatment. The short-term effects, changes of T lymphocyte subsets (CD3, CD4, CD8, CD4/CD8 ratio) and adverse reactions of the three groups were observed.

RESULTS: There was a significant difference in short-term effects among the three groups (P < 0.05), and the clinical improvement rate was significantly higher in the combination group than in the chemotherapy group and CIK group (86.2% vs 53.3%, 56.67%, P < 0.05), while there was no significant difference between the chemotherapy group and CIK group (P > 0.05). There were no significant differences in CD3, CD4, CD8, or CD4/CD8 ratio among the three groups before treatment (P > 0.05). After treatment, CD3, CD4, CD8, and CD4/CD8 ratio showed no significant changes in the combination group (P > 0.05), while CD3, CD4, and CD4/CD8 in the chemotherapy group and CIK group were significantly decreased (P < 0.05), and CD8 significantly increased (P < 0.05). CD3, CD4, CD8, and CD4/CD8 ratio were significantly better in the combination group than in the chemotherapy group and CIK group (P > 0.05). The rate of adverse reactions was significantly lower in the combination group and CIK group than in the chemotherapy group (17.2%, 10.0% vs 46.7%, P < 0.05).

CONCLUSION: The short-term effects of mFOLFOX6 chemotherapy combined with autologous CIK cells for patients with advanced colorectal cancer are remarkable, and the CIK cell therapy can avoid the functional disorder of T lymphocyte subsets induced by chemotherapy and is associated with fewer adverse reactions.

Species differences in tumour responses to cancer chemotherapy

Despite advances in chemotherapy, radiotherapy and targeted drug development, cancer remains a disease of high morbidity and mortality. The treatment of human cancer patients with chemotherapy has become commonplace and accepted over the past 100 years. In recent years, and with a similar incidence of cancer to people, the use of cancer chemotherapy drugs in veterinary patients such as the dog has also become accepted clinical practice. The poor predictability of tumour responses to cancer chemotherapy drugs in rodent models means that the standard drug development pathway is costly, both in terms of money and time, leading to many drugs failing in Phase I and II clinical trials. This has led to the suggestion that naturally occurring cancers in pet dogs may offer an alternative model system to inform rational drug development in human oncology. In this review, we will explore the species variation in tumour responses to conventional chemotherapy and highlight our understanding of the differences in pharmacodynamics, pharmacokinetics and pharmacogenomics between humans and dogs. Finally, we explore the potential hurdles that need to be overcome to gain the greatest value from comparative oncology studies.